rndis_wlan: copy only useful data from rndis_command respond

rndis_query_oid() uses full output buffer size to copy response buffer
from rndis_command()/device. This doesn't cause problems as response buffer
is sized based on output buffer but does copy extra unset bytes.
So change rndis_query_oid() so that only meaningful bytes are being copied.

Also in case of malfunctioning device/cable/etc returned data offset from
device might be wrong so bound check memory access correctly, so add
checks for this.

v2: fixed to use new netdev_dbg/warn/etc instead of old devdbg/warn/etc

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 29 insertions, 4 deletions

diff --git a/drivers/net/wireless/rndis_wlan.c b/drivers/net/wireless/rndis_wlan.c
index 9f6d6bf06b8e..a4f70de99cdd 100644
--- a/drivers/net/wireless/rndis_wlan.c
+++ b/drivers/net/wireless/rndis_wlan.c
@@ -704,6 +704,7 @@ static int rndis_query_oid(struct usbnet *dev, __le32 oid, void *data, int *len)
                 struct rndis_query_c    *get_c;
         } u;
         int ret, buflen;
+        int resplen, respoffs, copylen;
 
         buflen = *len + sizeof(*u.get);
         if (buflen < CONTROL_BUFFER_SIZE)
@@ -733,11 +734,34 @@ static int rndis_query_oid(struct usbnet *dev, __le32 oid, void *data, int *len)
                            le32_to_cpu(u.get_c->status));
 
         if (ret == 0) {
-                memcpy(data, u.buf + le32_to_cpu(u.get_c->offset) + 8, *len);
+                resplen = le32_to_cpu(u.get_c->len);
+                respoffs = le32_to_cpu(u.get_c->offset) + 8;
 
-                ret = le32_to_cpu(u.get_c->len);
-                if (ret > *len)
-                        *len = ret;
+                if (respoffs > buflen) {
+                        /* Device returned data offset outside buffer, error. */
+                        netdev_dbg(dev->net, "%s(%s): received invalid "
+                                "data offset: %d > %d\n", __func__,
+                                oid_to_string(oid), respoffs, buflen);
+
+                        ret = -EINVAL;
+                        goto exit_unlock;
+                }
+
+                if ((resplen + respoffs) > buflen) {
+                        /* Device would have returned more data if buffer would
+                         * have been big enough. Copy just the bits that we got.
+                         */
+                        copylen = buflen - respoffs;
+                } else {
+                        copylen = resplen;
+                }
+
+                if (copylen > *len)
+                        copylen = *len;
+
+                memcpy(data, u.buf + respoffs, copylen);
+
+                *len = resplen;
 
                 ret = rndis_error_status(u.get_c->status);
                 if (ret < 0)
@@ -746,6 +770,7 @@ static int rndis_query_oid(struct usbnet *dev, __le32 oid, void *data, int *len)
                                    le32_to_cpu(u.get_c->status), ret);
         }
 
+exit_unlock:
         mutex_unlock(&priv->command_lock);
 
         if (u.buf != priv->command_buffer)